Process of removing sulphur compounds from gases



Patented Mar. 8 1938 a TATES or REMOVING SULPHUR comrormns FROM GASES rnoonss 1 PAY 'I." orrics otio meien, Oberliausen-Holten; Germany, as

signor to Studien- .und Verwertnngsgeseilschatt m. b. H., Mulheim-Ruhr, Germany NoiDrawing. Application october 31, 1935, Se-

rial No. 47,636. ;In Germany November 5,1934

3 Claims. (01. 23-3) My invention relates to the removal of sul- V phur from gases. It has particular reference to the purification of gasmixtures containin CO and H by .the removal of the sulphurcom- 5 bined': with organic radicals which are admixed to these gases, and it is an objector my invention to. provide means,whereby this purification is rendered easierandmoreefiective than similar purification processes hithertoin use.

'As iswell known to those skilled intheart,

the removal ofall the sulphur, including that combinedwith organic radicals, from gasmixtures containing CO andHhashitherto been effected either by, catalytical decomposition of (i the organic sulphur compounds at a temperature above normal'followed by extraction of the hy- .drogen sulphide formedby this decomposition, or by directly combining these compounds with gas purification masses capable of absorbing ,sul-

- zphurat a temperature above normal.

, Either waywof operating the purification, in-

volves drawbacks of its own. While-it is true 3o instance for the catalytic hydrogenation of car- On the other hand the direct bon monoxide. extraction of the :sulphur by chemical combination at an elevatedtemperature, while allowing the removal-of all the sulphur excepting only 35 insignificant traces, requires a corresponding v 40 purification ofgas mixtures containing C0 and H in two stages, inthe first of which the bulk of the organic sulphur compounds isdecomposed in a. manner well known per se by catalytic reaction at an elevated temperature. I thereafter 45 prefer extracting the hydrogen sulphide formed in thereaction and then fix completely the whole of the remaining sulphur at an elevated temperatureby. means of chemicals which-absorb -.',su1'phur., p

50 I'thus succ eed in radically removing the sulphurfrom gas mixtures containing CO and H without their composition suffering any other change; Bythus; combining the two greatly dif iering modes oi purification I further obtain a 5 5 purification process which others quite a num ber ofadvantages as compared with each oi! these processes. i

The catalytic purification which iorms the first stage of myprocess is no morere'quired to remove the last traces of sulphur and I am there- 5 fore enabled to operate in this stage athigh gas velocities, so that the main quantity ofthe sul- Aphur can be extracted quickly. Furthermore I neednot fear that under the infiuence of a catalytic action cf the walls of the apparatus, such 1 l as the heat exchanger, organic sulphur compounds might be regenerated from C0 and H28 .when the gases leaving the apparatus cool down, and I am therefore at liberty to transfer to the entering gas and to thus recover without any. drawback the palpable heat of the gas treated in the first stage.

Furthermore, since it is not necessary that the decomposition be carried out in aquantitative manner, the gas may still carry along a. small percentage of hydrogen sulphide It is therefore possible to insert the catalytic'decomposition in the normal process or removal of .the hydrogen sulphide at a point where the main proportion of hydrogen sulphide has already been extracted. Therefore a separate extraction of hydrogen sulphide cannot only be dispensed with at'the end of theeatalytic purification stage, but I also recover, during the normal purification process by chemical combination with iron oxide or the like,

that part of they sulphur which wasoriginally present in the gas mixture in combination with organicradicals. c c

As regards the second stage of the process, the combined process according to this invention also offers a numberot advantages. Since, if the first stage is operated in a correct manner, 90% or more or the sulphur may be removed, the consumption or chemical purification ,mass in the second stage willbe low. Apart therefrom w I'have iound that this mass is now enabled to retain the last traces of sulphur in a far more perfect manner than it the first stage of the process were omitted. I have for instance round;

that when using purification masses consisting ofa mixture of an iron oxide andan alkali car- ,bonate, the emciency oi the mass up to the point .where the first traces'of sulphur appear in the gas escaping from the mass is the greaterthe lower the initial concentration of thegas. 5 Thus the technical eflect obtained by the combination of the two stages is far superior to. a purely additive eflect of the two individual stages. There are a number of gas mixturesincluding for instance coke oven gas, which it is impossible other of the two'operations separately, this being due to-the special nature of the compounds contained therein. For "instance heavy hydrocarbons present in these gas mixtures prevent a com-' plete decomposition of the organic sulphur compounds, from being obtained by mere 'oatalytical action; 'On' the other hand some'particularly resistive sulphur compounds such as thiophen are not converted into hydrogen sulphide by these tion of a mixtureof chemicals such as mentioned: above or by other chemical purificationmeans at z the relatively low temperature Voi vabout; 300 C., h at which this operation'lmustjbe carried through sinceat higher temperatures the chemicals vQvv'ould I bringabout an undesirable reduction of part; of

the carbon oxide to methane? 1 According to the present processit is possible to- In practising my invention I may for instance quantitatively free from sulphur also gases. of the kindhere mentioned, including coke oven-gaaby operatingthe-firststage at so high a temperature that the more resistive sulphur compounds are converted into "otherorganic or inorganic =comi pounds which can subsequntly' be extracted in i one of thetwo processes of sulphur ibration.

(Even stuns high temperature tne' catalys ilSed in the first stage of'the' process to jdec'omposethe; bulk oftheorganicsul'phur compounds, in oonstree s the purification-mass'usedin the second ftion-"ofmethanaf' I l v I H 1 Inorderto'jextract-the sulphur in the second stage I have found 'it particularly advantageous f "to operate'this'stage withfpurification masses "'5" which are capable of binding and removing all the sulphurat comparatively" low temperatures, I have found that masses containing, besides an, 'iron'oxida' also a; comparatively large "percentage s'tageg -do not bring about'any undesirable iormar of an alkali carbonate allow extracting-alsofthe last traces, of sulphur at temperature'sranging between 150 arid 300 '0. Such purifyingi masses are disclosed in the copending application tor-o, S;

' Letters Patent Serial No. 3094 filed'iJa'nuaryjl23,

1 935, "by jQtto"Roelen; and Walter 'Feiss't for Process fordesulphurizingjgasesi' Qn the other h'and 'the catalytic decomposition in the first stage always requires operation jata temperature 0,". about toenter the secohd stagei whichhave'been ruicooled down beforetojroo'm temperature in order I to allow thehydrogen sulphide toberemoved, a with theaid of warm heatinggases, which have 1am thus also enabledxto 71 m; name gases before been used heat up fresh gases entering thefirst stage.'f'I;-am therefore ina position to i keep the heat losseaat least in theffllt stage, I low'by heat exchang'e' between the entering and" the escaping'gases of reaction. as pointed out in ftheforegoing, this is'possible without any disadvantage owingtojthe purification in tW0"Stages.

Itis also possible to first pass "the gas in'fthe second stage in contact .wlthjthe "special purification mass mentioned; consisting forfinstance of eration thro h "in" the hydrogenation "apparatus ""proper,

Such a utilization, of the hydrogenation centage of sulphur, as decomposition first stage of the process chemical purification masses, after they have taken up a suflicient percatalysts at higher temperature. 7

I may therefore proceed with particular advantage in such manner that a body of purifica- -'tion mass is first usedfforextracting the last, traces of the sulphur still remaining in the gas mixture, whereupon'the same body of purifica-' 'tion mass is inserted in the corresponding phase ,;of the firstxstageot the process to be there saturated with sulphur, the temperature being at first held substantially constant for instance at 300 C., whereupon" the same body serves as decompositioncatalyst in the first stage of the process at a temperature whichis preferably raised for instance:to:400 C; It could notbe foreseen that the same 'inass' would be capable of such double proceed as follows:

'E'tdmpleL-Cmde watergas'is first freed from {all but thelast traces of hydrogen sulphide by passing -itinxion'tact with about two :thirds of =the quantity ofan iron oxide requiredlfor-the {complete extraction of all "the'hydrogen sulphide. 'Ihe'pg t1yApurIfied gas is now heated up in a heat exchanger by means of the heatvemitted by watergas leavingthe catalytic purification ap paratusand is thereafter by ;means of heating gases heated to '4'00" C. ina separate heater,

whereupon kit is treated with a 1' decomposition catalyst which may 1 consist for" instance -of sulphurizedirontturnings orsteel wool orof a mix- "tureof one part by weight Q cobaltv sulphide and two-parts molybdenum oxideglor ofnickel metal precipitated on a ceramic carrier. lt'lfhe, gas thereafter'fiows through the hcatexchang'er ,and is cooled to ro'om temperature zin a cooler, whereupon itis 'pass'ed in contact with the remaining third of the dry purification mass :for the removal of the hydrogen sulphide. 'I'he gas-is now heated up to 250 C'. by the'heat of the waste gases from the gas heater andis passed at this temperature across a granulatedpurification mass being a, mixture of two ipartsof a mass containing iron oxide (Lux mass) and one part soda. The -water- I g'as thus treatedywhileflbeing otherwise 'un-' changed, does not contain: any traces of sulphur which might' be ascertained by the usual'analytie EmmpZe'2.A mixturelof equal parts water- 'gas'and cokeoven gas is passed first through moist suspendediron oxide; thereafter through a'heat exchanger, through a beaten-M1450 C.

through a decomposition catalyst consisting of a spent mixture of 'Lux' mass andsoda' which hasabsorbed sulphur, again throughlthe heat exchanger, through a cooler, through another body ofLux mass for the removal ofihydrogen sulphide, 'througha gas heater suppliedtwlth the waste gases from" the first heater, thereafter'at230" C.

' thrdughhnother body of Lux mass and soda and -anfiron oxide'and'a large percentage of soda, at a fi y through 8 1 ro enat n a y (raised temperatureiand to' extract' thelast traces ,j'

of sulphur the aid ofl spent hydrogenation" catalysts, it being .even. possible to carry 'ppin order-to "be freed from -the"'.5 gram residual sulphur contained in 100 cubicm'etres of the-gas. frhistreatmentleads to a complete desulphura- 'tionof the gas. It requires only minimum quan- "disclosed in the foregoing specification} without departing from the invention or sacrificing the advantages thereof.

I claim: I 1. The multistage process of removing sulphur in organic combination from a gas mixture containing CO and H2, which comprises the steps of freeing such gas mixture from any substantial ,amount'of hydrogen sulphide, treating the gas mixture, for the decomposition of part of the organic sulphur compounds, with a catalyst possessing about the decomposing eflicacy of a sulphurized mixture of iron and soda, this treatment being carried out at a temperature above about 300 C., but lower than that at which, in the presence of the said catalyst, Hz would react materially with the CO present, removing part of the hydrogen sulphide formed in this treatment and passing the partly desulphurized gas mixture at a temperature ranging'between about 150 and 300 C. in contact with a mixture of iron oxide and a comparatively large percentage of an alkali metal carbonate.

2. The multistage process of removing sulphur in organic combination from a gas mixture containing 00 and H2, which comprises the steps of treating such gas mixture with iron oxide to remove any substantial quantity of hydrogen sulphide present, treating the gas mixture, for the decomposition of part of the organic sulphur compounds, at a temperature ranging between about 300 and 450 C. with the mixture of sulphurized iron oxide and alkali metal carbonate which results in another stage of the process, thereupon treating the gas mixture with iron oxide to remove part of the hydrogen sulphide formed in this treatment and passing the partly desulphurized gas mixture at a temperature ranging between about 150 and 300 C. in contact with a mixture of iron oxide and a comparatively large percentage of an alkali metal carbonate.

3. The process of claim 2 in which the gas mixture is further treated with a spent hydrogenation catalyst.

OTIO ROELEN. 

